There is an inkjet recording device connectable to an exchangeable main tank (also referred to as an ink cartridge), and ink is supplied from an exchangeable main tank to an ejection head of the inkjet recording device. The inkjet recording device ejects ink through the ejection head to form an image on a medium such as a recording sheet or other recording media. In the inkjet recording device, when a main tank is exchanged with new one after the ink in the main tank is used up, air may enter into an ink supplying path that leads to the ejection head. As an example of an inkjet recording device for preventing entry of air into the ink supplying path, JP-A-2002-307711 and JP-A-2005-66906 discloses a sub tank interposed between the main tank and the ejection head.
In this inkjet recording device, the sub tank is open to an atmosphere and connected to the ejection head via a flexible tube, and a main tank is mounted and connected to the sub tank from above. Even if the ink in the main tank is used up, ink remains in the sub tank. Therefore, the entry of air into the tube leading to the ejection head can be prevented. Also, although air may enter into a connection portion between the main tank and the sub tank during exchange of the main tank, since the sub tank is open to the atmosphere, the entered air moves along with the ink into sub tank and thereafter is separated from the ink due to its buoyancy and then discharged to the exterior. Accordingly, entry of the air into the tube can be prevented.